Method for producing purified oil and fat

Abstract

To provide a method for producing purified oil and fat wherein a reduction effect of harmful, low-volatility environmental pollutants contained in the oil and fat is significantly improved, and decomposition of DHA and EPA in the oil and fat is inhibited so that they remain in sufficient amounts.SOLUTION: There is provided a method for producing purified oil and fat for separating and removing low-volatility environmental pollutants from oil and fat, comprising a step of adding water to the oil and fat, a step of adjusting water concentration to 0.01-1.5%, and a step of performing thin-film distillation under conditions of 300 Pa or less and 200°C or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing refined fats and oils in which the amount of PCB, a harmful, low-volatile environmental pollutant contained in the fats and oils, is reduced. [Background technology]

[0002] Marine animal fats and oils such as fish oils including whale oil (hereinafter, for convenience in this application, simply referred to as marine animal fats and oils, including fish oils from freshwater fish) contain large amounts of highly unsaturated fatty acids such as eicosapentaenoic acid (hereinafter referred to as EPA) and docosahexaenoic acid (hereinafter referred to as DHA), and have been shown to have effects such as lowering blood neutral fats and cholesterol, as well as improving cognitive function, so it is recommended to actively consume highly unsaturated fatty acids. In addition, vegetable oils such as seed oils contain the highly unsaturated fatty acids α-linolenic acid and linoleic acid. In particular, α-linolenic acid can be used as a raw material to produce DHA and EPA in the human body, so it is also recommended to consume highly unsaturated fatty acids derived from vegetable oils. However, for example, in whales and fish, including saltwater fish and freshwater fish, which are near the top of the food chain in oceans and rivers, non-volatile environmental pollutants such as polychlorinated biphenyls (hereinafter referred to as PCBs), which are harmful to the human body and have been mixed into industrial water and released from rivers into the ocean, accumulate through so-called bioaccumulation. It is known that when PCBs accumulate when people ingest these, they can cause health problems such as general fatigue, numbness, and loss of appetite. In addition, typical electrical equipment containing PCBs has also been used or stored above ground, which has sometimes contaminated the soil. In the past, PCBs have also been mixed into vegetable oils and fats, causing skin symptoms such as pimples and pigmentation.

[0003] PCBs have become a social problem due to their toxicity and environmental and biological pollution, and their production and use have already been banned. However, PCB-containing transformers and capacitors continue to be used and stored, and there has been no clear reduction in PCB pollution of the environment or ecosystem. PCBs are highly lipophilic, so it is extremely difficult to reduce PCBs contained in oils and fats, in particular. Conventional oil and fat refining methods such as water washing, adsorption treatment, and steam distillation are hardly effective. Moreover, oils and fats have a significant impact on human life, as they are used as raw materials for food and cosmetics, so there was a need to develop technology to reduce PCBs in oils and fats. For example, Patent Document 1 discloses a production technique for marine oils and fats in which dioxins, including coplanar PCBs, are reduced by thin-film distillation. Furthermore, Patent Document 2 discloses a technique for efficiently removing compounds with relatively low boiling points, such as odorous components, by adding water to edible marine oil and then performing countercurrent steam distillation. Non-Patent Document 1 discloses a technique for reducing dichlorodiphenyltrichloroethane (hereinafter referred to as DDT) from cod liver oil, whale oil and other fish oils by molecular distillation. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2022-132317 [Patent Document 2] JP 2014-128273 A [Non-patent literature]

[0005] [Non-Patent Document 1] K. Julshamn, L. Karlsen and OR Braekkan, Fiskeridirektoratets skrifter; Serie teknologiske undersokelser, Vol. 5 No. 15 (1973) Summary of the Invention [Problem to be solved by the invention]

[0006] However, in Patent Document 1, thin-film distillation is performed in the range of 200°C to 270°C. Considering that DHA, EPA, or α-linolenic acid is likely to decompose in that temperature range, the invention disclosed in Patent Document 1 unavoidably decomposes highly unsaturated fatty acids such as DHA, EPA, and linolenic acid, and there was a problem that it was difficult to purify marine animal fats and oils or vegetable fats and oils while leaving these highly unsaturated fatty acids. In addition, in the invention disclosed in Patent Document 2, edible marine oil is prepared by countercurrent steam distillation at low temperatures, but there was a problem in that it was difficult to reduce the PCB content in the oil because PCBs are highly lipophilic.

[0007] The invention disclosed in Non-Patent Document 1 does not disclose anything about reducing low-volatile environmental pollutants such as PCBs, nor does it mention or suggest anything about inhibiting the decomposition of highly unsaturated fatty acids such as DHA, EPA or α-linolenic acid, so there is a problem in that it is not possible to reduce PCBs while leaving these highly unsaturated fatty acids intact. The present invention has been made to address such conventional problems, and aims to provide a method for producing refined oils and fats that can dramatically improve the effect of reducing harmful PCBs contained in marine animal oils and fats such as fish oils including whale oil, as well as animal oils and fats such as beef tallow, lard, chicken oil, horse fat, mutton tallow, vegetable oils and fats such as olive oil, sunflower oil, chia seed oil, palm oil, rice oil, etc., and processed oils and fats such as hydrogenated oils and fats, interesterified oils and fats, etc. The chemical structure of the oils and fats may contain polar lipids in addition to fatty acid triglycerides. Another object of the present invention is to provide a method for producing refined oils and fats that can reduce PCBs while preventing the decomposition of thermally unstable active ingredients, such as DHA and EPA contained in marine animal oils and fats, and linoleic acid contained in vegetable oils and fats such as seed oils, and allowing them to remain sufficiently. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, the first invention is a method for producing refined oils and fats, which is a method for producing refined oils and fats for separating and removing PCBs from oils and fats, and is characterized by comprising the steps of adding water to the oil and fats, adjusting the water concentration to 0.01 to 1.5% by weight, and performing thin-film distillation under conditions of 300 Pa or less and 200°C or less.

[0009] The second invention is a method for producing refined oils and fats according to the first invention, characterized in that the oil and fats are whale oil.

[0010] The third invention is a method for producing refined oils and fats according to the first invention, characterized in that ethylene glycol is used as a heat source in the thin film distillation step. Effect of the Invention

[0011] The method for producing refined oils and fats, which is the first invention of the present invention, separates and removes highly lipophilic PCBs from oils and fats, while being carried out at a low temperature at which the beneficial polyunsaturated fatty acids contained in the oils and fats, such as DHA, EPA, and α-linolenic acid, are not decomposed. Therefore, it is possible to purify the oils and fats without damaging them by suppressing the decomposition of these useful polyunsaturated fatty acids. Moreover, in the second invention, it is possible to exert the same effect on whale oil as in the first invention. In the third invention, by using ethylene glycol, which has a low boiling point of 197°C, as the heat source for thin-film distillation, it is possible to separate and remove PCBs while suppressing the decomposition of highly unsaturated fatty acids such as DHA, EPA, and α-linolenic acid. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a flow diagram of a method for producing refined oils and fats according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a conceptual diagram of a thin film distillation apparatus used in a method for producing refined oils and fats according to an embodiment of the present invention. [Diagram 3]1 is a graph showing the change in PCB concentration and the recovery rate of whale oil when whale oil is used as the oil, as an example of a method for producing refined oils and fats according to an embodiment of the present invention. [Figure 4] 1 is a graph showing the change in the residual rate of DHA and EPA when whale oil is used as the oil, as an example of the method for producing refined oils and fats according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, a method for producing refined oils and fats according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a flow diagram of a method for producing refined oils and fats according to an embodiment of the present invention, and FIG. 2 is a conceptual diagram of a thin-film distillation apparatus used in the production method. In FIG. 1, the method for producing refined fats and oils according to the embodiment includes step S1, which is a step of adding water to fats and oils to be refined. The amount of water added is small so that the concentration can be adjusted in step S2. Step S2 includes a step of adjusting the water concentration in the fats and oils to 0.01 to 1.5% by weight. In step S2, the water content of the fats and oils is measured using a Karl Fischer moisture meter or the like, and if the water content is low, water is added little by little. If the water content becomes high in step S2 or step S1, it is advisable to adjust the water content by removing the water by drying under reduced pressure or the like. Steps S1 and S2 may be performed simultaneously in parallel. In addition, while marine animal fats and vegetable fats are liquid at room temperature, animal fats other than marine animal fats are solid at room temperature. In such cases, it is advisable to provide an oil heating process prior to step S1 to raise the temperature of the oil and liquefy it before adding water.

[0014] The reason why water is added to fats and oils is that the inclusion of water in fats and oils produces the effect of steam distillation during thin-film distillation, which will be described later. That is, when water evaporates, the effect of evaporating PCBs, which are low-volatility environmental pollutants, is exhibited by azeotropy. If the amount of water in fats and oils is less than 0.01% by weight, the effect of steam distillation is difficult to achieve, and if it is more than 1.5% by weight, the evaporation of water reduces the heat source temperature of the thin-film distillation, inhibiting the evaporation of PCBs. In addition, the recovery rate of fats and oils is reduced due to the intense evaporation. Therefore, it is necessary to adjust the amount of water in fats and oils to 0.01 to 1.5% by weight. Step S3 is a process of thin-film distilling the oil or fat after the moisture adjustment. Thin film distillation is a process in which a distillate is brought into contact with a heat source at a high temperature under reduced pressure, the distillate forms a thin film, and non-volatile substances are separated from volatile and refractory substances. In this embodiment, fats and oils correspond to non-volatile substances, water corresponds to volatile substances, and PCBs, which are refractory environmental pollutants, correspond to refractory substances. An example of a thin film distillation apparatus used in step S3 will be described with reference to FIG.

[0015] In FIG. 2, thin film distillation apparatus 1 has distillation target inlet 2 at its upper end, through which the distillation target, that is, the fat or oil to be refined, is injected. Furthermore, the thin-film distillation apparatus 1 is equipped with a vacuum pump connection port 3, and by reducing the pressure inside the apparatus by drawing a vacuum, it is possible to further separate PCBs, which are low-volatility environmental pollutants. The higher the degree of reduction in pressure, the more effectively PCBs are separated, but as long as the pressure is lower than 300 Pa, separation can be performed without any problems. The fats and oils injected from the distillate inlet 2 flow into the spiral thin film forming flow path 4 formed inside the distiller 5 below, and while flowing downward through the thin film forming flow path 4, it is heated by the heater 6 formed inside, and PCBs, which are difficult to volatile substances, and water, which is volatile, are separated from the non-volatile fats and oils. The higher the temperature, the more efficient the separation of PCBs is expected to be, but since highly unsaturated fatty acids in fats and oils, such as DHA, EPA, and α-linolenic acid, which are active ingredients for the human body, are thermally unstable, it is necessary to perform thin film distillation at a low temperature, specifically 200°C or less.

[0016] DHA and EPA have multiple methylene groups with cis-type carbon-carbon double bonds at both ends of the molecule, while α-linolenic acid has three similar methylene groups, including the third from the ω end. In such cases, when heat is applied, the hydrogen of the methylene group is cleaved radically, and various reactions occur, such as isomerization to the trans form, conjugation, polymerization between molecules, and cleavage of carbon-carbon bonds, which reduces the content of DHA, EPA, or α-linolenic acid. This reduces the health benefits of the refined oil, so it is desirable to avoid thermal deterioration of the oil. Therefore, thin-film distillation at a low temperature of 200°C or less is necessary. In addition, when heating in the oil heating step in the first stage of step S1, the oil must be liquefied at a temperature that does not affect DHA, EPA, or α-linolenic acid. Specifically, the oil should be heated to about 30 to 55°C, which is the melting temperature of chicken oil, horse fat, lard, beef fat, mutton fat, etc.

[0017] The heater 6 receives a supply of boiled heat source stored in a heat source storage container 9 installed below the thin film distillation apparatus 1, and heats the oil from inside the thin film formation flow path 4. The heater 6 covers the thin film formation flow path 4 from the upstream side to the downstream side, and since the heat source is supplied from the side closer to the heat source storage container 9, a counterflow is formed with the oil flowing through the thin film formation flow path 4, and the lower part is heated to a higher temperature, accelerating the separation and removal of water and PCBs. Note that the high and low temperatures during heating in this embodiment are relative, and are "low temperatures" that do not damage DHA, EPA, or α-linolenic acid, and since this is a concept of relative temperature, it is of course possible to heat to a "high temperature" within that range. The thin film distillation apparatus 1 is provided with an atmospheric pressure release port 10 that communicates with the heat source storage container 9 and the heater 6, making it possible to maintain the boiling point of the heat source. As the heat source held in the heat source storage container 9, ethylene glycol, which has a low boiling point of 197° C., can be suitably used. The heat source is not limited to ethylene glycol, and any heat source may be used as long as it has a boiling point at atmospheric pressure that is not too low, that is, 200° C. or less, and is as close to 200° C. as possible, and can be used safely and stably without generating harmful vapors. For example, it may be an electric heater provided around the heater 6. In this embodiment, by adding an appropriate amount of water to the oil and fat and performing thin-film distillation, the effect of making it easier for the refractory substances to evaporate due to azeotropy when the water evaporates is achieved, making it possible to separate and remove PCBs, which are refractory environmental pollutants, from the oil and fat.

[0018] The next step S4 is a process for recovering the refined oil from which the PCBs have been separated and removed. In step S4, the separated PCBs are discharged from a PCB discharge port 7, and the oil refined by distillation is extracted from a refined oil extraction port 8. As explained above, in the method for producing refined fats and oils according to the present embodiment, an appropriate amount of water is added to fats and oils, and thin-film distillation is performed in a low-temperature, low-pressure vacuum environment that does not decompose or impair the contents of DHA, EPA, or α-linolenic acid, which are ingredients effective for the human body, and this makes it possible to evaporate PCBs, which are low-volatility environmental pollutants, as the water evaporates through azeotropy, and to separate and remove them from the fats and oils. Therefore, it is possible to purify fats and oils by separating and removing harmful PCBs while suppressing the decrease in the contents of DHA, EPA, or α-linolenic acid.

[0019] Next, as an example, an example will be described in which the oil is whale oil (minke whale oil), ethylene glycol is used as a heat source, and PCB, a low-volatile environmental pollutant, is separated and removed to produce refined oil. Note that the embodiment of the present invention is not necessarily limited to the following example, and can be freely modified within the scope of the invention.

[0020] <Example> Minke whale oil (hereinafter simply referred to as whale oil) was obtained by squeezing oil from commercially available minke whale skin at 150°C in the atmosphere and performing adsorption purification. Analysis of the minke whale oil before purification showed that the PCB content was 0.76 ppm, and the DHA and EPA contents were both 8.4% by weight. The amount of water added to the whale oil was adjusted to the water content shown in Table 1 within the range of 0.040 to 1.4% by weight as a parameter, and thin-film distillation was performed under conditions of boiling at atmospheric pressure using ethylene glycol as a heat source at a pressure of 266 Pa and a heat source temperature of 197°C. Note that the adsorption purification is a method in which silica gel is filled into a column, whale oil is poured in from the top, and the whale oil is sucked in from the bottom of the column with a vacuum pump and passed through the silica gel column to purify it. After refining, the amounts of PCBs, DHA and EPA contained in the refined whale oil, as well as the recovery rate of the refined whale oil, were measured. The changes in PCB content and recovery rate of the refined whale oil are shown in Table 1 and Figure 3. The recovery rate is a value given as the ratio of the weight of refined whale oil to the weight of injected whale oil. As a comparative example, whale oil was refined without adding water (water content 0% by weight) under the same pressure and heat source temperature. The results are also shown in Table 1 and Figure 3.

[0021] [Table 1]

[0022] As shown in Table 1 and Figure 3, in the case of whale oil to which no water was added as a comparative example, the PCB content was hardly reduced from the initial value (0.76 ppm) of the whale oil obtained by adsorption purification, whereas in the examples in which water was added, the effect of reducing the PCB content was dramatically improved. It was also found that even a small amount of moisture (0.040% by weight) added significantly reduced the PCB content, and that at a moisture content of 1.4% by weight, the PCB content could be reduced to approximately one-fortieth of the initial value. However, it is understood that the recovery rate tends to decrease as the amount of water added increases. This is because if there is a large amount of water, the water boils violently when it comes into contact with the heat source, causing some of the whale oil to splash onto the inner wall of the distiller 5 (see Figure 2). Also, the whale oil that is not recovered is discharged together with PCBs from the PCB discharge port 7 in Figure 2. Therefore, it is possible to perform thin-film distillation by selecting the amount of water to be added depending on whether the reduction of PCB content or the recovery rate is prioritized. Next, Table 2 shows the residual ratio of DHA and EPA in the refined whale oil obtained in this embodiment by thin film distillation with the amount of water added to the whale oil as a parameter. Table 2 is also shown in a graph in Figure 4, and the residual ratio of DHA and EPA will be explained with reference to these. The residual ratio is a numerical value given as the ratio of the weight of DHA or EPA in the refined whale oil to the weight of DHA or EPA in the whale oil before refinement.

[0023] [Table 2]

[0024] From Table 2 and Figure 4, it can be seen that when a water content of 0.040 to 1.4 weight % is added, the residual rate of DHA and EPA is generally higher as the amount of water added is less than the initial content (DHA 8.4 weight %, EPA 8.4 weight %) of the unrefined whale oil obtained by adsorption purification in the embodiment of the present invention. Even when the water content was increased to 1.4% by weight, the residual rate of DHA was 83% and the residual rate of EPA was about 93%, which is a difference of about 5-11% compared to the initial content, and it can be seen that the decrease in the content was suppressed compared to the initial content. Furthermore, it was found that the residual rate of EPA was higher, and that the rate of decrease of DHA with increasing water content was higher. When comparing the residual rate of DHA and EPA in the comparative example without adding water with the residual rate in the example, for example, when the water content of the example is 0.040% by weight, the residual rate is almost comparable. Note that the residual rate of EPA exceeding 100% is considered to be a measurement error. As explained above with reference to Tables 1 and 2 and Figures 3 and 4, in an embodiment of the present invention, an appropriate amount of water was added to whale oil, the temperature was kept low enough (197°C) that DHA and EPA would not decompose, and thin-film distillation was performed in a low-pressure vacuum environment, whereby PCBs, which are difficult to volatile substances, were evaporated along with the evaporation of water by azeotropy, and it was possible to separate and remove them from the whale oil. In other words, it was possible to purify whale oil by significantly separating and removing harmful PCBs compared to the case where water was not added, while suppressing the decrease in the content of DHA and EPA.

[0025] In this embodiment, minke whale oil was used, but other whale species, such as fin whale, sei whale, Bryde's whale, Antarctic minke whale, minke whale, Bryde's whale, and Eden's whale, can be used. In addition, the oils and fats are not limited to whale oil, and other animal oils and fats and vegetable oils can also be used to remove low-volatile environmental pollutants such as PCBs. Furthermore, marine animal fats and oils such as whale oil and fish oil contain large amounts of DHA and EPA, and even vegetable fats and oils such as seed oils contain large amounts of α-linolenic acid, so it is necessary to perform thin-film distillation at a low temperature so as not to decompose them, and therefore the method for producing refined fats and oils of this embodiment is of course suitable for this purpose. However, other fats and oils also have the same fatty acid triglyceride structure as whale oil and fish oil, and are thermally stable fats and oils if they do not contain DHA, EPA, or α-linolenic acid, so it is naturally possible to apply the method for producing refined fats and oils of this embodiment. [Industrial Applicability]

[0026] The present invention can be widely used as a method for producing refined oils and fats to separate and remove PCBs, a harmful, low-volatile environmental pollutant, while retaining the components contained in the oils and fats that are beneficial to the human body, such as DHA, EPA, and α-linolenic acid. [Explanation of symbols]

[0027] 1...Thin film distillation apparatus 2...Inlet for injecting distilled material 3...Vacuum pump connection port 4...Thin film formation flow path 5...Distiller 6...Heater 7...PCB outlet 8...Refined oil and fat extraction port 9...Heat source storage container 10...Atmospheric pressure release port

Claims

1. A method for producing refined fats and oils by separating and removing PCBs from fats and oils, comprising the steps of: adding water to the fats and oils; adjusting the water concentration to 0.01 to 1.5% by weight; and performing thin-film distillation under conditions of 300 Pa or less and 200°C or less.

2. 2. The method for producing refined fats and oils according to claim 1, wherein the fat and oil is whale oil.

3. 2. The method for producing refined oils and fats according to claim 1, wherein ethylene glycol is used as a heat source in the thin film distillation step.

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